decnet: use __dev_get_by_index instead of dev_get_by_index to find interface

The following call chain we can identify that dn_cache_getroute() is
protected under rtnl_lock. So if we use __dev_get_by_index() instead
of dev_get_by_index() to find interface handlers in it, this would help
us avoid to change interface reference counter.

rtnetlink_rcv()
  rtnl_lock()
    netlink_rcv_skb()
      dn_cache_getroute()
  rtnl_unlock()

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index ad2efa5..ce0cbbf 100644 (file)
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -1666,12 +1666,8 @@ static int dn_cache_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh)
 
        if (fld.flowidn_iif) {
                struct net_device *dev;
-               if ((dev = dev_get_by_index(&init_net, fld.flowidn_iif)) == NULL) {
-                       kfree_skb(skb);
-                       return -ENODEV;
-               }
-               if (!dev->dn_ptr) {
-                       dev_put(dev);
+               dev = __dev_get_by_index(&init_net, fld.flowidn_iif);
+               if (!dev || !dev->dn_ptr) {
                        kfree_skb(skb);
                        return -ENODEV;
                }
@@ -1693,8 +1689,6 @@ static int dn_cache_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh)
                err = dn_route_output_key((struct dst_entry **)&rt, &fld, 0);
        }
 
-       if (skb->dev)
-               dev_put(skb->dev);
        skb->dev = NULL;
        if (err)
                goto out_free;